The invention relates to a drive device for a machine for the plasticization and injection of synthetic material.
A drive device of this type is known, for example, from DE 100 28 066 C1. It is used in synthetic material processing machines which are designed as injection molding machines.
Their functioning can be divided into two main process steps. During the first, the plasticization of the synthetic material granulate supplied, an extruder worm is rotated and at the same time is moved axially rearward, that is to say away from an injection orifice. The synthetic material to be injected is thereby conveyed forward, while at the same time being heated and plasticized. During this, a counter force may also be necessary in order to implement a higher pressure during the plasticizing operation. The second main process step is the injection of the plasticized synthetic material into a molding die. In this case, the extruder worm is pushed axially forward.
In known drive devices, two drive motors and two associated converters, designed in each case according to the maximum torque occurring, are necessary. One motor takes over the rotational movement of the extruder worm and the other the forward push of the latter. Force transmission takes place, for example, by means of a ballscrew spindle with an associated spindle nut. The spindle body and the extruder worm connected to it are rotated by the first drive motor during the plasticizing step. The second drive motor corotates idly or generates counter pressure, as required. During the injection step, the first drive motor prevents a (reverse) rotational movement of the extruder worm, and the second drive motor rotates the spindle nut, with the result that the extruder worm is pushed forward. The process sequence described is thereafter repeated.